Patent GB-688965-A (GB)
Title: Improvements relating to means for the automatic control of the rates of emptying ofcontainers for liquids
Inventor: READ FREDERICK WILLIAM
IPC: G05D11/13
Filed: 1949-09-24
Abstract: 688,965. Automatic fluid level control systems. NATIONAL RESEARCH DEVELOPMENT CORPORATION. Sept. 25, 1950 [Sept. 24, 1949; Sept. 29, 1949], Nos. 24592/49 and 25068/49. Class 38 (iv). In a system for automatically maintaining equal the contents of liquid containers during emptying, electrical signals are derived proportional to the contents of individual containers and upon a predetermined difference between the signals, a relay-operated switch is actuated to adjust the rate of delivery from the containers to restore equality. In Fig. 1, the sliders of potentiometers P1-P4, connected across a D.C. source, are automatically adjusted in dependence on the percentage content of liquid containers T1-T4 respectively to produce corresponding energization of coils 17-20 of differential relavs 13-16. Opposing relay coils 21-24 are connected in parallel with one another and in series with coils 17-20 so that each is energized in accordance with the average percentage content of all the containers. The relays operate two-way switches 33-36 in a sense dependent on the relative energization of their coils to increase or decrease, through a further relay (not shown), the speed of individual motor-driven pumps delivering liquid from each container according to whether their associated containers have a content above or below average. In a modification the opposing relay coils are in series with each other instead of in parallel. The relays may only have one set of contacts so that correction is only by increasing the delivery from those containers having a content above average. A lock-out relay may be provided to isolate equipment associated with a tank having an abnormally large content due to a restriction in the delivery line. In Fig. 3, the sliders of potentiometers P1P-P5S are automatically adjusted in dependence on the content of port and starboard aircraft fuel tanks T1P-T5S, located as shown separately, and are connected in turn through a wiper S of a two-bank uniselector switch to energize a coil 55 of a relay 54 in dependence on the difference between the content of a selected tank, as determined by the slider potential and the average content of all tanks as determined by the potential of the common junction of resistors r connected to each slider. An opposing coil 53 of relay 54 is energized in accordance with the average content of all tanks. If the content of the selected tank is above average relay 54 does not operate and the uniselector dwells so that a wiper R of the other bank completes the operating circuit of a relay (not shown) to speed up the pump delivering from that tank. When the condition is corrected or if the content of a tank is below average relay 54 closes contacts 57, 58, thereby energizing relay 59 through periodically interrupted contacts 62, 63 and operating stepping magnet 61 to step the uniselector on. Undue dwell of the uniselector is prevented by a bimetallic element 68 operating contact 69 periodically, thus stepping the uniselector on through relays 70, 72. Content error is indicated by meter 73 on closing a manual switch 76 which may be ganged to a switch 75 operating the uniselector manually. In a modification involving a four-bank uniselector, one coil of relay 54 is energized by the difference in potential between successive pairs of potentiometer sliders, the tanks associated with which are chosen to avoid undue unbalance of the aircraft. The opposing coil of relay 54 is constantly energized. With this arrangement the delivery rate from a tank having a content above that of the tank with which it is compared is increased during dwell of the uniselector.